Pulse discriminator system



Dec. 4, 1951 c. H. SMITH, JR 2,576,975

PULSE DISCRIMINATOR SYSTEM Original Filed Dec. 10, 1945 CARL HARRISON SMITH,JR

Wm W mm m Av I... IN I. II w M II II II II m nm w R 0m 7 l L wumnom I: g i|| T II J wwq on b Q WEESE F 1. i m 5330 T M" U" 3 3% 3A" NEW m a M U" M Patented Dec. 4, 1951 PULSE DISCRIMINATOR SYSTEM Carl. Harrison Smith, Jr., Arlington, Va.

Original application December 10, 1945, Serial No.

634,128. Divided and this application September 25, 1950, Serial N 0. 186,621

(Granted under the act of March 3', 1883, as amended April 30, 1928; 370 0. G. 757) 2 Claims.

This invention relates to discriminator circuits for delivering an output signal upon the application thereto of a pulse type signal having a certain characteristic. Specifically the invention relates to pulse spacing discriminator systems wherein an output signal is delivered only upon the application thereto of a multiple pulse type signal wherein one pulse is separated from a subsequent plfls a predetermined time interval, and is a division of application N. 634,128, filed December 10, 1945, now U. S. Patent No. 2,541,038, granted February 13, 1951.

In the radio and the allied :art, interference between two or more signal sources is frequently encountered. This interferencemaybeminlmized by imparting a special transmission characteristic to the signal emitted by the desired signal source and providing certain selective characteristics in the receiving systems so that the receiving system is held solely responsive to the special transmission characteristic emitted by the desired signal source.

One special characteristic applicable in pulse type transmission is the emission of energy in the form of pulse groups, each group containing several pulses. Thus the spacing between the pulses of each group-can be accurately timed and such time interval made the basis of selection for delivery of output signals. In the reception of such a pulse signal, a special mechanism in the receiving unit is therefore required which is capable of rejecting single pulse signals or multiple pulse signals having a time spacing other than the desired amount.

It is therefore an object of this invention to provide a selector system responsive to multiple pulse signals in which the time interval between the first pulse of one signal group and a subsequent pulse of the same group is of a predetermined duration.

Another' object of the present invention is to provide a selector system which will deliver an output signal only upon the application to it of a pulse signal occurring a predetermined period of time after a previous pulse signal.

Another object of the present invention is to provide a pulse spacing discriminator in which the selective responding period may be adjustable as desired.

Other objects and features of the present: invention will become apparent upon a careful consideration of the accompanying drawing and detailed description.

In the drawing, the single figure of the drawing is a schematic diagram, partly in block, illustrating the features of the present invention.

With reference now to the single figure of the drawing, an apparatusis shown wherein a series of two positive pulses separated in time by a. known, predetermined amount are applied to the grid 29 of tube 39 from the multiple pulse source 3|. Tube 30 is normally maintained in a nonconductive condition due to the positive potential maintained at its cathode from the potential diwater 32, 3'3, placed between a source of positive potential and ground. Therefore a capacitance 34 connected. between the plate of tube 39 and ground is normally charged to the supply potential. A. first positive pulse applied to grid 29 causes tube 30 to conduct, discharging capacitance '34 to a potential as determined by'the voltage. divider action between resistance 35, the plate resistance of tube 39, and the positive potential normally maintained at the cathode of tube 30. At the conclusion of the positive pulse, tube 39 returns to a non-conductive condition and capacitance 34 begins to charge through resistance 35 producing. an exponentially changing or sawtooth voltage.

The exponentially changing voltage produced across capacitance 34 is applied through a coupling network including capacitance 36 to a second sawtooth generator circuit comprising a. switch tube 31, a charging capacitance 38 connected between the plate and cathode thereof, and a charging impedance 39 interposed between the plate of tube 31' and the positive supply. Tube 31 is normally possessed of near zero bias and is therefore conducting quite heavily; Thus a low positive voltage as determined by the voltage divider action between impedance 39 and the plate resistance of tube 37 is maintained across capacitance 38. The negative voltage produced at the plate of tube 39 as a first positive input pulse is received from source 3| changes this situation by stopping conduction by tube 31. Thereafter capacitance 38 begins an exponential charge toward the positive supply voltage through impedance 39.

A biased electron tube 40 is grid driven from the plate of tube 31. Normally tube 49 is maintained in a non-conductive state as a result of a high positive potential maintained at its cathode from a potential divider 4! connected between a positive supply and ground. As capacitance 38 charges positively, eventually the grid of tube 40 is raised to a point sufficiently high to permit conduction by the plate of tube 40.

Conduction of tube 49 results in the production of a negative voltage signal across the plate loading resistance 4|. This signal is applied to the grid of tube 43 of the coincidence establishing circuit 44 through a coupling circuit including capacitance 42A. The negative voltage signal applied to the grid of tube 43 interrupts a normally heavily conductive condition in tube 43 so that a'small voltage rise is experienced across the plate load resistance 45 whichis common to tube 43 and a second coincidence establishing tube 46. The relatively low plate resistance of tube 46, however, prevents any large rise in-voltage across resistance 45. This situation is quite difierent, however, if a negative voltage is applied to the grid of tube 46 at the same instant in time at which tube 43 is out off. Under this condition there will no longer be a voltage division between resistance 45 and the low plate resistance of the triode 3B. The potential at' the plates of tubes 43 and 46 will then show a large rise to the plate supply potential.

Tube 46 receives inverted pulses obtained from source 3| through an inverter tube 4'! provided for that purpose. Tube 4'! is normally maintained in a non-conductive condition by the connection of its cathode to the voltage divider 32, 33, however, in response to positive input pulses, tube 4'! is brought to conduction to produce negative pulses across the plate loading resistance 48. These negative pulses are ap lied to the grid of tube 4-6 by means of a coupling circuit including capacitance e9. Thus in a manner as previously described, simultaneous a plication of signals to the grids of tubes '43, 46, will result in the produc tion of large amplitude positive signals across their common plate loading resistance 45.

Simultaneous occurrence of the second positive ,pulse from source 3| and the negative pulse from the plate of the tube 4! will be realized only if the time delay produced by the charging of capacitance 38 is sufiicient to cause the initiation of conduction by tube 4!! during the interval in time in which the second pulse occurs.

tions of the potentiometer 4| which varies the bias voltage maintained on tube 40. Actually the charging of capacitance 34 does not enter into the time determination provided that tube 49 returns to conduction before tube 31. Such a condition is insured by the proper selection of the values of time constant elements 34, 35, as well as 38, 39, and the bias voltage on tube 40. Thus under this condition, the second pulse signal of the two pulse series renders tubes 3!) and 41 conducting but will not affect tube 3'! so that charging of capacitance 38 is unaffected. To make the triggering action more positive it is desirable to have the coupling circuits including capacitances 42A and 49 of the short time constant variety toproduce peaked.keying signals for application to circuit 4-4.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A multiple pulse group discriminator for delivering an output signal whenever two pulses of a multiple pulse signal group occur with a desired time spacing, comprising; a first sawtooth voltage generator circuit, means initiating the production of a progressively varying voltage by said first This .time delay is made readily adjustable by variasawtooth voltage generator circuit in response to a first input pulse of the multiple pulse signal group, a second sawtooth voltage generator circuit operably connected to said first circuit for producing a second progressively varying voltage in response to the first input pulse signal, a biased electron tube connected to the output of the second sawtooth voltage generator circuit operative to produce a pulse type timing signal when the second progressively varying voltage reaches a predetermined amplitude after a predetermined period of time, a coincidence establishing system for producing large amplitude signals upon simultaneous application thereto of two separate pulse signals of selected polarity and amplitude, first differentiating coupling means connecting the coincidence establishing system and the biased electron tube, and coupling means including a second differentiating network applying the multiple pulse signal groups to the coincidence system.

2. A decoding system providing response to a pulse group signal wherein each successive pulse signal of the group is delayed in time from the the first pulse of the group by a known amount, comprising; a first capacitive energy storage device, a first electron tube connected to the first capacitive energy storage device, said first electron tube biased to partially discharge said first capacitive energy storage device in response to input pulse signals applied thereto, a potential connection providing a positive su ply volta e, a resistive path connected to the first capacitive energy storage device and to said potential connection permitting an exponential recharging of the first capacitive device after the conclusion of each input pulse, a second capacitive energy storage device, a second electron tube connected to said second capacitive energy storage device and to the first capacitive energy storage device operative to hold said second capacitive energy storage device in a partially charged condition whenever the first capacitive storage device is fully charged, a current limiting impedance connected to said second capacitive energy storage device, to the second electron tube and to the potential connection permitting the fiow of energy to said second capacitive storage device when said second electron tube is cut-off, electron tube means connected to said second capacitive energy storage device producing a pulse type signal when the progressively varying voltage across said second capacitive energy storage device reaches a predetermined value after a predetermined period of time, and a coincidence circuit connected to said electron tube means for producing an output signal when said pulse type signal and a second input pulse signal occur in time coincidence.

CARL HARRISON SMITH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,277,000 Bingley Mar. 17, 1942 2.534364 Hoeppner Dec. 19, 1950 

